A phase detector is a circuit which compares the phase of one signal with the phase of another. One common application is in phase lock loops where the phase detector is coupled in a loop with a filter and a voltage controlled oscillator. This circuit can be used to control the frequency and phase of a desired signal.
Most phase detection for use with serial data require a full baud dock. One example of a phase detector is a Hogge detector. This circuit works by splitting the data bit into two and measuring the width of the two halves. An example of this type of circuit is disclosed in the paper found on page 1736 of IEEE JSSC, volume 27, number 12, December 1991, incorporated herein by reference.
Another phase detector is the sampling phase detector. This circuit produces a beat note which is utilized in the phase detection process. An example of a sampling phase detector is described in the paper found on page 1747 of IEEE JSSC, volume 27, number 2, December 1992, incorporated herein by reference.